Macrowine 2021
IVES 9 IVES Conference Series 9 Fractionation of copper and iron in wine: Assessment of potential macromolecule and sulfur binding agents

Fractionation of copper and iron in wine: Assessment of potential macromolecule and sulfur binding agents

Abstract

Copper and iron are known to substantially impact wine stability through oxidative, reductive or colloidal phenomena. However, the binding of metal ions to different wine components under wine conditions, and the impact of this binding on the ability of the metal ions to induce spoilage processes, is not well understood. This study surveyed a range of red and white wines for an understanding of the variability of broad metal categories within the wines. The techniques utilized included an electrochemical constant current stripping potentiometry technique (ccSP), and solid phase extraction (SPE) fractionation of wine with subsequent analysis of the metal content of each fraction by inductively coupled plasma – optical emission spectroscopy (ICP-OES). The binding efficiency of specific classes of wine macromolecules and wine sulfur compounds for copper(II) and iron(II) was also assessed, and related to the metal categories found in the surveyed wines. The wine macromolecules examined included isolated white wine protein, white wine polysaccharide, red wine polyphenols (including procyanidins and monomeric phenolic compounds), and white wine polyphenols. The sulfur compounds included hydrogen sulfide, methanethiol, glutathione and thiol-substituted phenolic compounds. For the volatile sulfur compounds, the free and bound-forms were also measured by gas chromatography with sulfur chemiluminescence detection (GC-SCD). The binding was assessed by mixing the wine components with copper (II) (0.4 mg/l), iron (II) (3 mg/l) and two different metal ion mixtures (Fe 3 mg/l + Cu 0.4 mg/l and 3 mg/l + 0.2 mg/l) in a model wine system (pH 3.2) in low oxygen wine conditions. The results showed that in the wines surveyed the metal ions had significant variability in fractionation, with a higher proportion of bound copper than iron. From the binding studies, it was found that a component of the red wine polyphenol wine fraction demonstrated evidence of interaction with both copper and iron, whilst hydrogen sulfide was a significant binder of copper. Importantly, the binding between hydrogen sulfide and copper was shown to be reversible in wine conditions. The other wine macromolecules did not show any significant binding to the metal ions. The results demonstrate an important insight into the predominant forms of iron and copper ions in wine, and also insight into the main binders, especially from the perspective of wine macromolecules.

Publication date: May 17, 2024

Issue: Macrowine 2016

Type: Oral

Authors

Nikolaos Kontoudakis*, Andrew Clark, Eric Wilkes, Geoffrey Scollary, Mark Smith, Paul Smith

*CSU/NWGIC

Contact the author

Tags

IVES Conference Series | Macrowine | Macrowine 2016

Citation

Related articles…

Impact of industrial-scale serial filtration on macromolecules in red wines

Filtration is a critical step in ensuring the clarity and microbial stability of wine prior to bottling. However the process of filtering potentially reduces red wine quality by removing some of the macromolecules that contribute to the texture of the wine. Commercial red wines, Cabernet Sauvignon (CAS) and Shiraz (SHZ), of two vintages and two grades (premium grade wines from the older vintage: CAS13 and SHZ13; and standard grade wines from a younger vintage: CAS14 and SHZ14) were filtered through industrial-scale commercial filtration units prior to bottling. Samples were taken before and after cross-flow filtration, lenticular filters, 0.65 µm and 0.45 µm pore size nylon membrane filters. The concentration and composition of macromolecules, including tannins and polysaccharides, were measured in all samples as well as particle size distribution and wine colour.

Study of the content of amino acids and biogenic amines in sparkling red wines

The production of red sparkling wines is lower in Spain in comparison with the winemaking of white or rosé sparkling wines. In red sparkling wine processing it is essential to obtain suitable base wines that should have moderate alcohol content, high acidity, good color values, an adequate mouth-feel and a sweet tannin. Grapes for sparkling wine production have to be harvested at low maturity stages, with lower alcohol contents and higher acidities, which will that the phenolic maturity of the grapes is also low, showing green tannins. This paper analyses different treatments in order to minimize these inconveniences: cold maceration-prefermentation and delestage to elaborate the grapes with lower maturity, must nanofiltration, and the partial osmosis of the wines made from grapes with an adequate maturity degree.

South Africa’s top 10 Sauvignon blanc wines. How do the chemical and sensory profiles compare?

FNB Top 10 Sauvignon Blanc competition, presented by the Sauvignon Blanc Interest Group of South Africa and sponsored by First National Bank, is the country’s foremost platform for producers of this cultivar to showcase and benchmark their wines. Wines entered in the competition originated from all over the winegrowing regions of the country and the winning wines showed good representation of quality South African Sauvignon blanc wines. The ten selected wines were subjected to various chemical analyses including volatile thiol and methoxypyrazine determination, while the sensory profile of each wine was determined using projective mapping.

Accumulation of polyphenols in Barbera and Nebbiolo leaves during the vegetative season

Grapevine berries produce thousands of secondary metabolites of diverse chemical nature that have been largely detailed in the past due to their importance for defining wine quality. The wide Vitis vinifera diversity, resulting in thousands of different varieties well detailed in many studies regarding berries, is still not investigated in vegetative organs, leaves in particular. Deepening knowledge related to this aspect could be of great interest for many reasons (for example the possibility of using leaf extract for pharmaceutical, cosmetic and nutrition purposes) but, above all, for understanding the susceptibility of different grapevine varieties to pathogens.

Light-struck taste in white wine: enological approach for its prevention

Light-struck taste is a defect prevalent in white wines bottled in clear glass light-exposed for a considerable amount of time leading to a loss of color and appearance of sulfur-like odors. The reaction involves riboflavin (RF), a highly photosensitive compound that undergoes to intermolecular photoreduction by the uptake of two electron equivalents from an external donor, the methionine. The reaction includes different steps forming methional which is extremely unstable and decomposes to methane thiol and acrolein. The reaction of two molecules of methane thiol yields dimethyl disulfide. Methane thiol is highly volatile, has a low perception threshold (2 to 10 µg/L in wine) and confers aroma-like rotten eggs or cabbage.